Spin fluctuations and superconductivity in layered $f$-electron superlattices

We investigate magnetic and superconducting properties of layered $f$-electron superlattices within the fluctuation exchange approximation (FLEX). We show that spin fluctuations, which are characterized by the maximum value of the spin susceptibility in the 3-dimensional (3D) Brillouin zone, are strongly suppressed in $f$-electron superlattices. However, effective 2D spin fluctuations can be increased due to the spatial confinement of the $f$-electrons. Therefore, the tendency towards $d_{x^2-y^2}$-wave superconductivity, mediated by these spin fluctuations, can be strongly increased in $f$-electron-superlattices. This is in sharp contrast to superlattices composed of conventional $s$-wave superconductors, where superconductivity is generally suppressed.